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SUMMARY:Inverse estimation of fibre reinforced soft tissue of human gallbl
 adder wall - *Luo\, X\, Li\, W\, Hill\, N (University of Glasgow/Sheffield
 )
DTSTART:20111212T163000Z
DTEND:20111212T170000Z
UID:TALK34917@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Cholecystectomy (surgical removal of the gallbladder) for gall
 bladder pain is the most common elective abdominal operation performed in 
 the western world. However\, the outcome is not entirely satisfactory as t
 he mechanism of gallbladder pain is unclear. We have developed a mechanica
 l model of gallbladder aiming to understand its mechanical behaviour. To a
 pply this model to clinical situations\, it is often necessary to estimate
  the material properties from non-invasive medical images. In this work\, 
 we present a non gradient-based optimization inverse approach for estimati
 ng the elastic modulus of human gallbladders from ultrasound images. Two f
 orward problems are considered. One utilizes a linear orthotropic material
  model and tracks the Elastic moduli in the circumferential and longitudin
 al directions. The other is a nonlinear Holzapfel-Grass-Ogden model in whi
 ch two families of fibres are embedded circumferentially in an otherwise h
 omogeneous Neo-Hookean elastin matri x. These forward problems are solved 
 using the finite element package Abaqus\, and a python/Matlab based optimi
 zation algorithm is developed to search the global minimum of the error fu
 nctional\, which measures the difference in geometries from the numerical 
 predictions and images. We will compare and analyse the results for six ga
 llbladder samples\, and discuss the outstanding challenging issues.\n
LOCATION:Seminar Room 1\, Newton Institute
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